The referenced prior patent application discloses a humidification and evaporative cooling system in which a modulating valve placed in the water supply line of the system is opened and closed in response to an air signal to restrict or increase the flow of water to in duct spray heads in order to satisfy humidification and evaporative cooling requirements.
The present invention improves on the system in the prior application by providing a new and better method of modulating the water discharge from the spray heads, whereby each spray head can be individually modulated. In the new technique, the modulation is accomplished by pressurizing the rear chamber of each air and water spray head with control air. The modulating water valve disclosed in the prior application is eliminated from the control section of the improved system in accordance with the present invention.
In accordance with the present invention, in response to a demand for humidity, the control section of the system operates to open the air and water solenoid valves in the air and water supply lines so that air and water can flow to the in duct spray heads. A separate pneumatic control system delivers a pneumatic pressure signal to a fitting connected in the rear chamber of each system spray head. As the pneumatic pressure signal to the rear of each spray head, behind its diaphragm, is increased or decreased, such signal will off-set or counteract a part of the water pressure acting on the forward side of the diaphragm. As the differential between the control air pressure and water pressure on the opposite sides of the spray head diaphragm is increased or decreased, it will cause the spray head plunger mechanism controlling the outlet of water to shift rearwardly or forwardly, thereby increasing or decreasing the flow of water through that particular spray head.
Therefore, once air and water flow to a spray head of the system is established, a decreasing pneumatic pressure signal will allow the plunger in each spray head to retract or open further, thereby permitting an increased flow of water through the spray head. As the system modulates downwardly, the control air pressure in the rear of the spray heads is increased, causing the plunger to move forwardly, in turn causing the water flow in the head to be restricted and the output of water from the head to be correspondingly diminished.
Among the advantages derived from this new method of air modulation of the system are the following:
(1) The previous method of modulating the system with a water modulating valve had an operational range of only 2-3 psi water pressure, whereas the improved method of modulation has an operational range of 10 psi control air pressure.
(2) The proportional air/water output from the spray heads can be much more precisely controlled, with no hysteresis, and absolutely positively shut off.
(3) The previous method of modulation was limited to a system having a minimum capacity of 120 lbs/hr of water, while the improved method is unlimited in the sense that a single spray head can be modulated, or a manifold containing 100 or more spray heads could be modulated.
(4) By adjustment of the tension of the plunger spring in the rear chamber of each spray head, the modulation range can be adjusted. For example, in a manifold having two heads, one head can be adjusted to operate from zero to full capacity over a range of 0-10 psi pneumatic signal input. The second spray head on the manifold could be adjusted to operate from zero to full capacity over the range of 10-20 psi pneumatic signal input. This enables the installation of a manifold which can have several stages of operation from a single 0-20 psi pneumatic signal input. In the prior method, multiple manifolds were required to achieve multiple stages of operation in the system.
(5) The improved method of modulation additionally allows the mounting of spray heads at different elevations while being supplied from the same control section of the system. Previously, all heads of a single system required mounting at exactly the same level, to avoid differences in water column pressure.
The system according to the prior referenced application is most suitable where large capacities of 200 lbs./hr. or more are involved. In such systems, the use of a water modulating valve may be preferable. However, generally speaking, systems having capacities under 200 lbs./hr. should be modulated pneumatically, and without the use of a water modulating valve, in accordance with the present invention.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description. Generally speaking, the present invention has the same objectives and abilities set forth in the prior application for an in duct atomizing humidification and evaporative cooling system.